RFR: 8366240: Improve memory ordering in new CPU Time Profiler

[Johannes Bechberger]

Remove acq-rel semantics where it isn't needed.

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Commit messages:
 - Remove unnecessary line
 - Remove redundant synchronization

Changes: https://git.openjdk.org/jdk/pull/26960/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26960&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366240
  Stats: 34 lines in 2 files changed: 5 ins; 9 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/26960.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26960/head:pull/26960

PR: https://git.openjdk.org/jdk/pull/26960